In the last two decades of research on high speed sewing a much greater understanding of the complex interactions involved in joining two or more plies of material with thread has been achieved. It should be appreciated that although almost 150 years has now passed since the invention of the sewing machine, rigorous scientific analysis of the operation thereof did not begin until sewing machine speeds increased beyond about 3000 stitches per minute. At this sewing speed, the number of problems related to sewability increases due both to the higher speeds and the newer types of textile materials being joined together. More specifically, finer gauge knitted fabrics, fabrics processed with new dyes and finishes, and the widespread acceptance of synthetic fibers in both fabrics and sewing threads creates new sewability problems, particularly at the new high sewing speeds in excess of 3000 stitches per minute.
Researchers have previously investigated the aforementioned high speed sewing problems with a wide range of testing instruments and recommended a number of ways to minimize the problems. However, as the apparel industry becomes ever more automated, the sewing machine will be subjected to new manufacturing requirements since the operator thereof will no longer have direct control of the material being sewn in the machine. In future apparel manufacturing environments the sewing machine will be required to be more flexible in order to perform equally efficiently in processing a wide range of materials.
A substantial proportion, if not the majority, of previous material sewability testing has been conducting utilizing a strain gauge secured to the underside of the throat plate of a sewing machine. This type of testing system generally provides comparative needle penetration force data, but a clarity of force data is difficult to obtain since the throat plate is subjected to forces from the presser foot as well as needle penetration forces. Efforts have been made in the past to minimize presser foot force influences by using an alternative feeding mechanism, but when this technique is used the practical value of data obtained is severely limited due to the modification of the sewing system being studied.
Also, other researchers in attempting to test sewability and obtain an understanding of the forces relating thereto have failed to provide good resolution of forces at high sewing speeds. As is known to those skilled in this art, the prior testers' results tended to lose clarity of force resolution at about 2000 stitches per minute. Thus, testers have continued the search for a better understanding of the forces involved in high speed sewing of materials and the development of equipment to measure these forces.